linux-kernel - Re: [PATCH v4 3/3] randomize_kstack: Unify random source across arches

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Message-ID: <20260121102017.539b5531@pumpkin>
Date: Wed, 21 Jan 2026 10:20:17 +0000
From: David Laight <david.laight.linux@...il.com>
To: kernel test robot <lkp@...el.com>
Cc: Ryan Roberts <ryan.roberts@....com>, Catalin Marinas
 <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Huacai Chen
 <chenhuacai@...nel.org>, Madhavan Srinivasan <maddy@...ux.ibm.com>, Michael
 Ellerman <mpe@...erman.id.au>, Paul Walmsley <pjw@...nel.org>, Palmer
 Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, Heiko
 Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, Alexander
 Gordeev <agordeev@...ux.ibm.com>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen
 <dave.hansen@...ux.intel.com>, Kees Cook <kees@...nel.org>, "Gustavo A. R.
 Silva" <gustavoars@...nel.org>, Arnd Bergmann <arnd@...db.de>, Mark Rutland
 <mark.rutland@....com>, "Jason A. Donenfeld" <Jason@...c4.com>, Ard
 Biesheuvel <ardb@...nel.org>, Jeremy Linton <jeremy.linton@....com>,
 llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 loongarch@...ts.linux.dev, linuxppc-dev@...ts.ozlabs.org,
 linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org
Subject: Re: [PATCH v4 3/3] randomize_kstack: Unify random source across
 arches

On Wed, 21 Jan 2026 07:50:16 +0800
kernel test robot <lkp@...el.com> wrote:

> Hi Ryan,
> 
> kernel test robot noticed the following build warnings:
> 
> [auto build test WARNING on akpm-mm/mm-everything]
> [also build test WARNING on linus/master v6.19-rc6 next-20260119]
> [cannot apply to tip/sched/core kees/for-next/hardening kees/for-next/execve]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Ryan-Roberts/randomize_kstack-Maintain-kstack_offset-per-task/20260119-210329
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
> patch link:    https://lore.kernel.org/r/20260119130122.1283821-4-ryan.roberts%40arm.com
> patch subject: [PATCH v4 3/3] randomize_kstack: Unify random source across arches
> config: x86_64-allmodconfig (https://download.01.org/0day-ci/archive/20260121/202601210752.6Nsv9et9-lkp@intel.com/config)
> compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260121/202601210752.6Nsv9et9-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@...el.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202601210752.6Nsv9et9-lkp@intel.com/
> 
> All warnings (new ones prefixed by >>):
> 
> >> vmlinux.o: warning: objtool: do_syscall_64+0x2c: call to preempt_count_add() leaves .noinstr.text section
> >> vmlinux.o: warning: objtool: __do_fast_syscall_32+0x3d: call to preempt_count_add() leaves .noinstr.text section  
> 

When CONFIG_DEBUG_PREEMPT or CONFIG_TRACE_PREEMP_TOGGLE is set
the preempt_count_[en|dis]able() calls inside [put|get]_cpu_var()
become real functions.

Maybe __preempt_count_[inc|dec]() can be called (with this_cpu_ptr()).

	David